
        html,
        body{
            height: 100%;
            overflow: hidden;
        }
        .center{
            position: absolute;
            top: 50%;
            left: 50%;
            transform: translate(-50%,-50%);

        }
        #root{
            width: 300px;
            height: 300px;
            background: green;
            position: absolute;
            top: 50%;
            left: 50%;
            transform: translate(-50%,-50%);

        }
        .outer{
            width: 200px;
            height: 200px;
            background: orange;
        }
        .inner{
            width: 100px;
            height: 100px;
            background: blue;
        }